Study On The Mechanism And Effect Of Interaction Between Water Retention Agent And Different Fertilizers

In order to study the interaction mechanism and effect of water-retaining agent and different fertilizers,four particle size water retaining agents and 7 fertilizers（nitrogen,phosphorus,potassium,iron,manganese,zinc,copper）were selected to study the adsorption and slow-release law of the absorption time and initial mass concentration of the water retaining agent on nutrients.On this basis the slow release and utilization efficiency of the water retaining agent in the soil for nutrient elements were studied,and the effect of the water retaining agent combined with nitrogen and phosphorus fertilizers on soil nutrients and corn growth through field cultivation experiments were studied.It could provide a basis for the development of water retaining agent functional materials that improve the utilization of a large amount of fertilizer and the effectiveness of micro-fertilizers,the reasonable selection of particle size and their application in agricultural production.（1）The water absorption rate of the water-retaining agent decreased with the increase of the initial mass concentration of the fertilizer.A subtractive function model could be used to characterize the relationship between different fertilizer concentrations and the water retaining agent water absorption rate;The divalent cations in fertilizer ions had a greater impact on the water absorption performance of the water retaining agent.（2）The ion exchange and complexation of the functional groups of the water retaining agent played an important role in the adsorption of various fertilizer ions.The equilibrium adsorption capacity of the four particle size water retaining agents for different initial mass concentrations of fertilizers all increased with the increase of the initial mass concentration.It conformed to the Freundlich isotherm adsorption model.The equilibrium adsorption capacity in descending order was NH₄⁺>K⁺>Zn²⁺、Fe²⁺、Cu²⁺、Mn²⁺>H₂PO₄^-,that is,the adsorption effect of the water retaining agent on monovalent cations was better than that of divalent cations than anions,and the equilibrium adsorption capacity of water retaining agents of different particle sizes was expressed as particle size L₁、L₂>M、L.The unit adsorption capacity of the four particle size water retaining agents for fertilizers all increased with the increase of time,and finally the adsorption capacity gradually stabilized to reached the relative equilibrium of adsorption,and the adsorption process all conformed to the quasi-secondary kinetic model.The results of the fertilizer release test showed that the larger particle size water retaining agents L₁ and L₂ had better sustained-release effects under the same conditions.（3）The leaching test showed that there was a significant difference in the total volume of the water retaining agent with the same particle size and different dosages,and the increase in the amount of water retaining agent,the better the soil moisture retention effect;The same amount of water retaining agent with different particle size had the best effect on soil moisture retention performance of particle size L₂and L₁.Regarding the amount of leaching,the leaching amount of fertilizers（nitrogen,potassium,iron,manganese,zinc,copper）treated with water retaining agent was lower than that without water retaining agent,and the amount of water retaining agent increased,the amount of leaching decreased,and the fertilizer retention capacity was improved.The leaching amount of phosphate fertilizer increased with the increased in the amount;the larger particle size water retaining agent had the best effect on the maintenance of nitrogen,phosphorus,potassium,manganese,zinc,and copper fertilizers in the soil,and the best water and fertilizer maintenance effect.（4）The application of water retaining agent significantly reduced the soil bulk density of 0-30cm soil layer,and significantly increased the soil porosity of 0-20cm soil layer;for the aggregate content,after applying the water-retaining agent to the soil,the content of small-particle aggregates was reduced and increased the content of large-particle aggregates,that is,the distribution of soil aggregates was changed.The combination of water retaining agent+fertilizer increased the content of total N,quick-acting N,all P,quick-acting P,all K,quick-acting K and organic matter in the soil,and had the best effect on soil fertility enhancement.The combination of water-retaining agent+fertilizer could promote plant growth and improve the emergence rate,plant height,ground diameter,taproot length and leaf area index.